The present invention relates to an image forming apparatus which has a photosensitive body for forming an electrostatic latent image thereon and which visualizes the image with a developer and, more particularly, to an image forming apparatus which cleans with a cleaning blade the residual developer on the surface of a photosensitive body.
In an image forming apparatus such as an electrostatic copying apparatus, a nontransferred toner remaining on the surface of a photosensitive drum is generally scraped off with a cleaning blade to clean the photosensitive drum.
If a relatively great frictional force acts between the photosensitive drum and the cleaning blade, the surface of the photosensitive drum may be damaged or filming of the toner may result; stress acting on the blade may deteriorate the desired contact state to cause turning-up; and, static electricity generated by friction results in non-uniform surface potential in the charging step, which, in turn, causes an irregular image formation or fogging. In order to reduce the frictional force, the pressure of the cleaning blade may be reduced. However, if these measures are taken, the cleaning blade may not be able to function well for its original purpose, that is, cleaning, or the problem of filming may recur.
In order to reduce the frictional force acting between the cleaning blade and the photosensitive drum while maintaining a predetermined pressure of the cleaning blade, it has been conventionally proposed to add a lubricant such as wax to the toner. However, in this case, due to the presence of the lubricant in the toner, fixability of the toner may be degraded or filming may also be caused. This significantly degrades the image quality and renders this proposal impractical.
It has also been known to manually apply a lubricant such as wax on the surface of the photosensitive drum. However, no method has been proposed which is capable of maintaining the thickness of the lubricant film formed on the photosensitive drum for a long period of time within a range of below several hundred angstroms so as not to interfere with the electrostatic characteristics of the photosensitive drum. Attempts have also been made to construct the cleaning blade with a material having a low coefficient of friction. However, these attempts are also subject to the problem of degradation in other characteristics, especially mechanical strength, due to the addition of additives.